Washington has held several joint exercises with allies South Korea and Japan this year, and deployed three aircraft carriers to the area
He reiterated his claims that the North was a nuclear state and insisted its expansion of the weapons programme was a defensive measure.
Government says it is concerned about the increasing tension in the Korean Peninsula but has not yet issued any travel advisories to South Africans.
South Korea’s President Park Geun-hye has called for North Korea to walk away from nuclear weapons and take the "peace and shared development" path.
China is likely to agree to new sanctions on its ally, North Korea as its frustration grows after it defied bans to conduct its third nuclear test.
Iran successfully test-fired a long-range, improved Sejil 2 missile on Wednesday, state television reported.